The data structure should consist of the minimum possible number of objects, especially when you use high-level objects like a Vector or a Hashtable. These classes provide significant functionality but are not efficient storage mechanisms and you should avoid using them in the persistent store if possible.

When possible, use primitives instead of objects, because primitives reduce the number of object handles that are consumed on the BlackBerry device. An array of primitives is an object and consumes an object handle.

String objects are as efficient as byte arrays. A String object consumes only one object handle and is equivalent if your application stores all of the characters as a byte. In other words, the value of each character is less than or equal to the decimal value of 255. If your application cannot store characters as a byte, you can store the characters as a String because it is equivalent to storing a char array.